A: Sunlight is made up of small particles of energy called photons. Photovoltaic (PV) systems use semi-conducting materials such as silicon to absorb some of these photons and transfer them to electrons. This process is known as the photoelectric effect and it is the basic physical process by which PV cells convert sunlight to electricity. Special electrical properties of the PV cell – a built-in electric field – provide the voltage needed to drive the current through an external load (such as a light bulb).

A: Energy conversion efficiency is an expression of the amount of energy produced in proportion to the amount of energy consumed, or available to a device. The Sun produces a lot of energy in a wide light spectrum, but we have so far learned to capture only small portions of that spectrum for conversion to electricity using photovoltaics. Today’s commercial PV systems are about 7% to 17% efficient. By comparison, a typical fossil fuel generator has an efficiency of about 28%. However, some experimental PV cells now convert nearly 40% of the energy in sunlight to electricity.

A: For a growing number of users, particularly those who are environmentally aware, renewable energy is the clear choice. Solar provides sustainable energy, operates silently, produces no toxic emissions or greenhouse gases, and causes no hazardous waste. Renewable energy systems generate electricity using the Sun’s free energy, wind, or water, so the ongoing costs are minimal. Moreover, continued R&D means installation costs are gradually being reduced. Some people would rather invest capital on an energy-producing improvement to their property than continually send money to a power company. Others like the security of reducing the amount of electricity they buy from power utilities, because it makes them less vulnerable to power outages and future increases in the price of electricity.

A: Renewable energy can be used to power your entire home’s electrical systems, including lights, cooling systems, and appliances. For example, solar systems today can be blended easily into both traditional and non-traditional homes. The most common practice is to mount modules onto a north-facing roof or wall (in the southern hemisphere). For an additional aesthetic appeal, some modules resemble traditional roof shingles and tiles or can be built right into glass skylights and walls.

A: Renewable energy systems can be blended into virtually every conceivable structure for commercial buildings. You will find PV being used outdoors for security lighting as well as in structures that serve as covers for parking lots and bus shelters, generating power at the same time. Architects can use building-integrated PV to design buildings that are environmentally responsive, aesthetically pleasing, and produce their own power. Building-integrated PV provides a dual-use building material, reduces renewable energy system costs by using the building as the mounting or support structure, and reduces utility bills through on-site power production.

A: A 10% efficient PV system will generate about 180 kilowatt-hours per square meter. A PV system rated at 1 kilowatt will produce about 1800 kilowatt-hours a year. Allowing for a loss of efficiency of less than 1% per annum, such a PV system could generate close to 36,000 kilowatt-hours of electricity over 20 years and close to 54,000 kilowatt-hours over 30 years. This means that a solar system generates more than US$10,000 worth of electricity over 30 years.

A: A solar energy system needs unobstructed access to the sun’s rays for most or all of the day. There is enough sunlight to make solar energy systems useful and effective almost anywhere in the world. Most homes have adequate roof space for a solar system, and this can be complemented by integrating the system into walls or by using modules to cover a porch or patio in the backyard.

A:The size of solar system you need depends on several factors-such as how much electricity or hot water or cooling you use, how much sunshine is available where you are, the size of your roof, and how much you’re willing to invest.

A: Solar energy technologies often have a higher initial cost outlay. This means that a person is likely to pay more money up front to purchase and install a solar system. Still, in nearly all cases, the high initial cost is recovered through substantial energy savings over the life of the product (15-30 years).

A: The benefits of solar cars are obvious – they don’t pollute, and free sunlight is their fuel. The drawbacks are that, using today’s technology, a solar car has to be very lightweight for the panels to provide enough energy to power the car at road speeds, and it has to have enough battery storage to travel long distances without sunlight (at night and on overcast days). As part of continued research and development, many organizations are improving the systems used in solar cars to make them more efficient and cost effective. Some car companies are making great strides in this area with the new petrol/electric hybrids, and future progress is likely to be rapid.

A: The energy from the Sun is critical to all life on Earth. Evolutionary scientists have shown that the Sun’s energy played an essential role in ‘spontaneous generation’, whereby the very first single-cell amoebae split and developed into more complex lifeforms. Plants require sunlight for the process of photosynthesis or the production of sugars, and a by-product of the photosynthetic process is cellular respiration, which releases the oxygen that we must have to stay alive. All types of animals, including humans, also rely on the sun’s heat to maintain body temperatures and sustain life. Thankfully, the Sun has sufficient helium mass to provide the Earth with energy for another 5 billion years.

A: The word ‘photovoltaic’ essentially means electricity from the energy of sunlight. First used in about 1890, the word has two parts: photo, derived from the Greek ‘phos’ meaning light, and volt, a unit of measurement named for Alessandro Volta (1745-1827), a pioneer in the study of electricity.

A: There are four main types of solar energy technologies:
1. Photovoltaic (PV) systems, which convert sunlight directly to electricity by means of PV cells made of semiconductor materials.
2. Concentrating solar power (CSP) systems, which concentrate the sun’s energy using reflective devices such as troughs or mirror panels to produce heat that is then used to generate electricity.
3. Solar water heating systems, which contain a solar collector that faces the sun and either heats water directly, heats a ‘working fluid’ or heats air that, in turn, is used to heat water.
4. Transpired solar collectors, or ‘solar walls’, which use solar energy to preheat ventilation air for a building.

A: A PV system is made up of several different components. These include groups of PV cells called ‘modules’ (also known as panels‘); one or more batteries; a charge regulator or controller for a stand-alone system; an inverter for a utility-grid-connected system or when alternating current (AC) rather than direct current (DC) is required; wiring; and mounting hardware or a framework.

A: A PV system that is well designed, installed and maintained can operate for more than 20 years. The basic PV module has no moving parts and can last more than 30 years. The best way to ensure and extend the life and effectiveness of your PV system is by having it properly installed and well maintained.

A: PV systems are generating clean power in a whole host of applications right across the world – from urban skyscrapers and military installations to remote villages in developing countries. PV electricity can be used to power all manner of household appliances, computing and communications equipment, water pumping and lighting. Cost-effective examples of lighting powered by PV include small garden lights, street lights, lighting for recreational areas, highway signs, warning signs and signals, and lighting for businesses and homes. Virtually any power need can be met with PV.

A: Worldwide carbon emissions are currently at some staggering 16 million tons every 24 hours, and global energy consumption is expected to increase at an alarming rate every year.
• The Sun has sufficient helium mass to provide the Earth with energy for another 5 billion years and, every 15 minutes, it emits more energy than humankind uses in an entire year.
• The Earth receives only one half of one billionth of the Sun’s radiant energy, but, in just a few days, it gets as much heat and light as could be produced by burning all the oil, coal and wood on the planet.
• The Sun represents 99.8% of the total mass of our solar system, its surface temperature is 6000ºC, and its total energy could melt an ice cube the size of planet Earth in just 30 minutes.
• The sun provides and has provided all the energy that we use.
• Worldwide, some 2 billion people are still without electricity and, for these populations, it is more economically viable to install solar panels than to extend established electricity grids.
• By using renewable energy systems, we are bypassing the millions of years that it takes to create the conventional fuel sources that are used today.
• It is reported that the earth’s reserves of oil will run out within the next 50 to 70 years.

In more recent times, the environmental costs of burning fossil fuels have seen the world’s interest in solar energy systems gather even further momentum. With issues such as global warming and carbon emissions now scientifically proven and firmly on the political agenda, the demand for photovoltaic technologies is set to continue apace.

A: A major driver in the deployment of renewable energy is public demand for clean energy. Fossil-based energy pollutes the environment, and nuclear energy creates hazardous waste. If we stop to consider the environmental and health costs of fossil-fuel and nuclear energy, then renewable energy makes sense. So, in the coming decades, we will begin to see many more solar energy systems being built in areas that now use fossil fuels and nuclear energy for electricity generation. In developing countries, where there is little or no supply system for conventional energy, renewable energy is already being used because it is much less expensive than many other options, and the environmental benefits associated with this cleaner form of energy are significant.

A: Contrary to some popular notions, the landscape of a world relying on PV would be almost indistinguishable from the landscape we know today. There are three reasons for this. First, PV systems have siting advantages over other technologies. They can be put on roofs and can even be an integral part of a building, such as a skylight. Second, even ground-mounted PV collectors are efficient from the perspective of land use. Flat-plate PV technology is the most land-efficient means to produce renewable energy. Third, adequate sunlight is ubiquitous and often abundant, and present in predictable amounts almost everywhere

For example, in the United States, cities and residences cover about 140 million acres of land. The nation’s energy requirements could be met simply by applying PV to 7% of this area – on roofs, on parking lots, along highway walls, on the sides of buildings, and in other dual-use scenarios. Not one single acre of new land would need to be appropriated to make PV the primary energy source.

A: Solar Energy has been around for a lot longer than people realise. The first Solar Photovoltaic Effect was discovered in 1839 by a 19-year-old French Physicist name Edmond Becquerel. His discovery seemed small at the time, however laid the platform for solar power as we know it today.

Here are some more key milestones in the rise of Solar Power today:
• 1976 The NASA Lewis Research Centre starts installing 83 photovoltaic power systems across the globe, to provide vaccine refrigeration, room lighting, medical clinic lighting, telecommunications, water pumping, grain milling and classroom television.
• 1977 Worldwide photovoltaic production exceeds 500 kilowatts.
• 1982 Volkswagen of Germany begins testing photovoltaic arrays mounted on the roofs of Dasher station wagons, generating 160 watts for the ignition.
• 1983 Worldwide photovoltaic production exceeds 21.3 megawatts.
• 1985 The University of South Wales breaks the 20% efficiency barrier for silicon solar cells under 1-sun conditions.
• 1992 A 7.5-kilowatt prototype dish system using an advanced stretch membrane concentrator becomes operational.
• 1994 The first solar dish generator using a free-piston Stirling engine is connected to an existing utility grid.
• 1996 The world’s most advanced solar-powered airplane, the Icare, with 3,000 super-efficient solar cells, flies over Germany.
• 1999 Worldwide photovoltaic production exceeds 1000 megawatts.
• 2000 Astronauts at the International Space Station begin installing solar panels on what becomes the largest solar power array deployed in space.
• 2002 Japan installs 25,000 solar rooftops on homes throughout the country.
• 2003 Global investment in solar and wind power exceeds US$20 billion per annum.
• 2006 Worldwide photovoltaic production exceeds 1,744 megawatts.

A: Energy Assurance
In this day and age of technology we depend, almost critically, on a constant flow of electricity. Without it, our economic, political and social infrastructures are thrown into chaos.

As an example of this, the Amazon. COM company loses $1 million each minute when a power disruption makes its website unavailable. As worldwide demand for energy continues to rise exponentially, systems designed for the expected loads and capacities of yesteryear are prone to failures such as power outages and wide scale blackouts.

What’s more, many forms of conventional electricity production – from oil fields and gas pipelines, to nuclear power plants and hydro-electricity stations – are vulnerable to a wide range of natural disasters, as well as vandalism, sabotage and acts of war or terrorism.

Renewable energy systems, on the other hand, allow us peace of mind with regard to electricity supply. They provide us with a highly reliable, low-cost source of power, and can operate independently in homes, office towers, shopping malls, administrative centres and government.

A: It certainly does!
Every day, more and more people across the globe are seeking ways in which they, as individuals can contribute to a cleaner, greener future for our planet. If you are considering solar power for domestic use, we commend you and hope the information provided here allows you to make an informed judgment about PV systems.

Renewable energy has almost no environmental impact: Studies show that more than one third of consumers are willing to pay at least $10 per month more for energy sources that do not harm the environment. As a clean and silent energy alternative, PV systems produce no atmospheric emissions, greenhouse gases, noise pollution or hazardous waste.

A: Here are several standout features about Solar Power that sell themselves:

Renewable energy is a highly reliable source of electricity:
Renewable energy offers an independent energy source, and can keep electricity flowing during power outages. Today’s state-of-the-art Renewable energy systems have been so refined that they can generate sufficient power in all weather conditions – even on extremely overcast days.

Renewable energy systems are very low-maintenance:
Because modern solar systems have no moving parts and are stress-tested for such things as hail impact and high wind cycles, occasional visual checks and battery services are all the maintenance required.

Renewable energy costs very little to operate:
Obviously, Solar systems use sunlight to produce electricity, so the energy source is free. Once installed, solar panels generate electricity with little upkeep and minimal operating costs.

A: Certainly not! Solar power systems are now architecturally designed: Bulky and intrusive solar power panels are a thing of the past. Today’s streamlined solar modules – available in a variety of colours and styles – are, in fact, used as architectural design elements and can be seamlessly incorporated into roofs, skylights, awnings, entrances and facades.

A: Everywhere you look across the globe, renewable energies are changing the way we think:

Global Economy
New business models and political paradigms are recognizing the economic benefits of embracing alternative energy sources. This is because alternative energy, including Solar Power, can play an important role in delivering greater economic prosperity in Western countries and the developing world.

In Developed Economies:
By reducing the world’s dependence on fossil fuels, renewable energy systems contribute to stabilizing energy prices and, in turn, to moderating the transport cost component of commodities and mineral resources. Both of these factors are proven to be intrinsically linked to improved consumer confidence and economic growth.

Given that they draw on a free and constant energy source, renewable energy systems are also helping to enhance the reliability of power grids and reduce the costs to business of power outages. In the U.S. alone, blackouts are estimated to cost the economy more than $119 billion a year.

In addition, solar energy now supports an industry all of its own and provides hundreds of thousands of jobs across the globe. With demand growing at around 25% per annum over the past 15 years, associated industries such as engineering, science, architecture, construction, planning and industrial design now generate significant revenue from renewable energy development.

In Developing Economies:
One of the fastest-growing markets for solar power systems is in providing electricity to villages in developing countries, where the cost of extending existing utility grids is prohibitive. The provision of a free and plentiful electricity source via solar power has a resoundingly positive economic impact, both within these countries and for those nations providing foreign aid.

By delivering power for water supply, refrigeration, lighting, medical clinics and other basic needs, solar power is contributing enormously to the improvement of health and hygiene in hundreds of the world’s remote villages. Moreover, many of these villages are gaining the benefits of improved literacy, education and communications.

The result of solar power installations in developing nations is a reduced reliance on economic and humanitarian aid, and an ability to reduce the foreign debt of third world countries, where as much as 90% of export earnings are used to pay for imported oil.

A: Yes it can! Solar Energy emits no greenhouse emissions into the atmosphere, which is one of the major impacts in relation to Climate Change.

Climate change is a rapidly advancing human crisis that threatens millions of lives, natural species and the environment, according to leading international scientists.

The Intergovernmental Panel on Climate Change – a group of thousands of renowned international scientists who provide authoritative advice on climate change – predicts drastic negative effects if climate change continues at its historic levels, including:
• Increased risk of extinction for up to 30% of the world’s natural species by 2020 and total extinction of 40% of the world’s species by 2080.
• Increased natural disasters – such as flood, wildfire and storms.
• Increased mortality from heat waves, floods and droughts.
• Destruction of coral reefs and melting of polar regions, raising sea levels by 13 to 20 feet.
• Millions of deaths worldwide and enormous increases in poverty and hunger.

Climate change is caused by the build-up of carbon dioxide and other greenhouse gas emissions in the atmosphere. Carbon dioxide is produced by human activities such as employing industrial processes, using fossil fuels as an energy source and destroying forests which assist in removing carbon dioxide from the atmosphere.

To address climate change we must dramatically reduce our greenhouse gases emissions, primarily by moving away from traditional sources of energy to more efficient and renewable sources. This requires understanding and commitment at all levels – including government, business and individuals.

A: Advantages of Pure Sine Wave inverters over modified sine wave inverters:
a) Output voltage wave form is pure sine wave with very low harmonic distortion and clean power like utility-supplied electricity.
b) Inductive loads like microwave ovens and motors run faster, quieter and cooler.
c) Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, Game consoles, Fax, and answering machines.
d) Prevents crashes in computers, weird print out, and glitches and noise in monitors.
e) Reliably powers the following devices that will normally not work with modified sine wave inverters:
   • Laser printers, photocopiers, magneto-optical hard drives
   • Certain laptop computers (you should check with your manufacturer)
   • Some fluorescent lights with electronic ballasts
   • Power tools employing “solid state” power or variable speed control
   • Some battery chargers for cordless tools
   • Some new furnaces and pellet stoves with microprocessor control
   • Digital clocks with radios
   • Sewing machines with speed/microprocessor control
   • X-10 home automation system
   • Medical equipment such as oxygen concentrators

Modified Sine Wave works well for most uses, and is the most common type of inverter on the market, as well as the most economical. Pure Sine Wave inverters (also called True Sine Wave) are more suited for sensitive electrical or electronic items such as laptop computers, stereos, laser printers, certain specialized applications such as medical equipment, a pellet stove with an internal computer, digital clocks, bread makers with multi-stage timers, and variable speed or rechargeable tools (see “Appliance Cautions” below). If you wish to use those items with an inverter, then choose a Pure Sine Wave inverter. If you mostly want to run lights, TV, microwave oven, tools, etc, a Modified Sine Wave inverter is fine for your needs.

We often are asked if computers will work with Modified Sine Wave. It’s been our experience that most (with the exception of some laptops) will work (though some monitors will have interference such as lines or a hum). However, if you have any doubt about any appliance, tool or device, particularly laptop computers and medical equipment such as oxygen concentrators, we recommend that you check with its manufacturer to be sure it is compatible with a Modified Sine Wave inverter. If it is not, choose one of our Pure Sine Inverters instead.

The difference between them is the Pure Sine Wave inverter produces a better and cleaner current. They are also considerably more expensive. You might find it practical to get a small Pure Sine Wave inverter for any “special need” you may have, and also a larger Modified Sine Wave inverter for the rest of your applications.

Appliance Cautions:
DO NOT plug small appliances into the inverter AC receptacles to directly recharge their nickel-cadmium batteries. Always use the charger provided with that appliance.

DO NOT plug in battery chargers for cordless power tools if the charger carries a warning that dangerous voltages are present at the battery terminals.

Not all fluorescent lamps operate properly with an inverter. If the bulb appears to be too bright, or fails to light, do not use the lamp with an inverter.

Some fans with synchronous motors may slightly increase in speed (RPM) when powered by an inverter. This is not harmful to the fan or to the inverter.

Certain rechargers for small nickel-cadmium batteries can be damaged if plugged into an inverter. In particular, two types of appliances are susceptible to damage:

Small, battery-operated appliances such as flashlights, cordless razors and toothbrushes that can be plugged directly into an AC receptacle to recharge.
Certain battery chargers for battery packs that are used in some cordless hand-tools. Chargers for these tools have a warning label stating that dangerous voltages are present at the battery terminals.
DO NOT use an inverter with the above two types of equipment.

The majority of portable appliances do not have this problem. Most portable appliances use separate transformers or chargers that plug into AC receptacles to supply a low-voltage DC or AC output to the appliance. If the appliance label states that the charger or adapter produces a low-voltage DC or AC output (30 volts or less), there should be no problem powering that charger or adapter.

SPI acknowledges information provided by the U.S. Department of Energy (www.eere.energy.gov) as source material for this section of the website.